It used to be assumed (taken for granted) among Christians, that the coming of Jesus Christ made the world a better place in some ultimate sense; and that conversion of a person or nation to being Christian did much the same.
But I regard it as a fact that - spiritually - the world now is much worse than was the world 2000 years ago; because there has never before been so much (and top-down, official, propagandized, mandatory) inversion of true values.
I regard Christianity as essentially about the next world, not this-world; so its effects on this-world are secondary to changes in attitudes and expectations consequent upon the desire for salvation. It is the desire for salvation - and also the expectation - that constitute the main societal effect of Christianity; and this main effect has manifested very differently among Christians of different types, times and places.
Standing where we are, in 2023 and in The West; we find a world that has not just turned away from Christianity, but turned against it.
Like it or not; the societal agendas of Christianity (and the other religions) have been subverted, corrupted... and are now largely subordinated-to, indeed assimilated-into, an international leftist, atheist, materialist ideology.
A Christian now stands largely alone, or with a handful of companions; in a world where institutions (including churches) are actively net-evil - or else in present danger of becoming-so.
The fact of Christianity's failure to make the world a better place ought not to surprise anyone whose faith is rooted in the Fourth Gospel - but that has not been the basis of Christianity (which, in practice, is rooted in the Synoptic Gospels, the Epistles, or church theology and tradition).
When it became a church-focused, church-mediated, religion; Christianity almost-inevitably became primarily social. The church agenda was more often mainly up-front about this-wordly behaviour; and only much more secondarily and remotely about resurrection and Heaven.
Indeed, Christianity has often become millennialist in its nature; and focused upon this-world being saved and redeemed by a second coming of Jesus Christ - implicitly acknowledging that Jesus only half-succeeded in his mission, and needed to come-back in order to finish the job.
This, as I say, was partly a consequence of the expectation that Christianity implied that the world - this mortal world - would become a better place: indeed a perfect place. The coming of Jesus from heaven to Earth was taken to mean that a process had-been initiated by which the Earth would (by some combination of gradual and radical change) become Heaven.
Well, as I said above; not only has this not (yet?) happened after 2000 years - but (IMO) this-world is further from Heaven, than ever before in the history of Mankind. Realistically, therefore, Christianity is now an individual-level religion - essentially 'about' the spiritual relationship between the individual Christian and Jesus Christ... Or else (if society is regarded the index of success) Christianity is a failure, and looks set to become worse.
Another aspect of the two millennium span since the time of Jesus Christ is that Men have changed from being immersed in their group identities, to being very-much individuals. Insofar as modern Men have group identities, these are chosen (and often changed).
In the past, Men lived essentially as part of various groups they were born-into or socialized-into; much of their behaviour was spontaneous and driven by unconscious group factors; and their choices were merely amounted to 'take it or leave it', and were very much buried in those identities.
Indeed, this immersive unconsciousness is probably why a church based Christianity was inevitable 2K years ago. It simply did not make sense (it was not a matter of awareness) to Men of that era, that an individual could and did exist primarily apart from the groups into-which he has been born... And therefore (because he has-chosen) that each Man's religion just-is now his own responsibility.
Nowadays, this alienated individualist state (sometimes termed alienation) has gone from being the subject of vast comment and discussion, to being simply taken for granted and unavoidable.
So; these are two great conclusions that I draw from the past 2000 years:
First that Christianity is not primarily about the world, but about each individual Christian; and second that nowadays (like it or not) we experience ourselves primarily as individuals.
I said these seem like 'facts' to me; but of course that isn't really accurate: I see them as assumptions that are unavoidable when I am honest with myself.
And this forms the basis, my foundation, of that way of being a Christian that I (and a few others) term Romantic Christianity.